Non-shortening wrapped balloon

ABSTRACT

A non-shortening catheter balloon having a longitudinal axis and an inflatable balloon able to be affixed to a catheter shaft is provided. The balloon has an uninflated length which remains relatively unchanged upon inflation and is formed of least two helically oriented wrapped passes of balloon materials at a balanced force angle. Methods of making this balloon are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of commonly owned andco-pending U.S. patent application Ser. No. 11/501,249, filed Aug. 7,2006.

BACKGROUND OF THE INVENTION

The present invention relates to balloon catheters and, moreparticularly, to a non-shortening wrapped balloon configured to expandwith essential radial symmetry to a predetermined diameter uponapplication of a predetermined pressure thereto.

Balloon catheters are well known in the art. Such catheters are employedin a variety of medical procedures, including dilation of narrowed bloodvessels, placement of stents and other implants, and temporary occlusionof blood vessels.

In a typical application, the balloon is advanced to the desiredlocation in the vascular system. The balloon is then pressure-expandedin accordance with a medical procedure. Thereafter, the pressure isremoved from the balloon, allowing the balloon to contract and permitremoval of the catheter. The balloon must be formed of a material whichhas a low profile to allow entry through a vessel, yet is readilypressure-expanded and able to contract upon removal of the inflationpressure.

Procedures such as these are generally considered minimally invasive,and are often performed in a manner which minimizes disruption to thepatient's body. As a result, catheters are often inserted from alocation remote from the region to be treated. However, previous wrappedballoons have suffered from problems such as overexpansion duringinflation and shortening of the balloon due to inflation resulting inunreliable placement of the balloon in a vessel. This is particularlyconcerning when large diameter balloon are employed in medicalprocedures because the maximum hoop stress of the inflated balloonmaterial can more easily be exceeded causing the balloon to rupture orburst.

Previous attempts to compensate for overexpansion have been made.

However, only the present invention provides a non-shortening balloonthat expands to a maximum diameter in an essentially radial symmetricfashion. While an advantage of a low angle wrapped balloon is that thewrap is accomplished at the deflated diameter making mounting to acatheter shaft possible. The balloon then inflates to a larger diameterin use at which time the wrap angle rotates to the neutral angle. Atypical low angle wrapped balloon will foreshorten as it is expanded.Compensation for foreshortening by means ofaccordion-scrunching-length-storage is limited in that the longitudinalfolds push out and then the angle moves to the neutral angle thus theforeshortening is not eliminated during inflation. The devices andmethods of the present invention minimize foreshortening whilemaintaining an essentially radial inflating balloon, and allow theballoon to be mounted on a smaller diameter catheter shaft. The presentinvention solves the clinical issues of accurate placement of a balloonor stent due to foreshortening of traditional wrapped balloons. Thepresent invention also prevents undue trauma on vessel endotheliallayers and possibility of plaque fragmentation caused by inflationmovement of asymmetric inflating balloons.

SUMMARY OF THE INVENTION

The present invention is a balloon catheter comprising a catheter shafthaving a longitudinal axis and an inflatable balloon affixed to saidshaft, said balloon having an uninflated length which remains relativelyunchanged upon inflation and comprising at least two helically orientedlayers oriented at a balanced force angle.

A non-shortening wrapped catheter balloon having a longitudinal axis,comprising a first balloon material layer fused to a second balloonmaterial layer is provided, wherein the first balloon material isoriented at an angle of less than or equal to about 55 degrees and thesecond balloon material is oriented at an opposing angle of less than orequal to about 55 degrees with respect to the longitudinal axis. Theseopposing angle layers create a balloon preform.

A method of creating a non-shortening catheter balloon with increasedburst pressures is provided, said balloon comprising: wrapping a mandrelwith an anisotropic film at a low angle to form a balloon preform;removing the mandrel; exposing the balloon preform to internal pressureat a temperature to soften or a melt point for the film or imbibingmaterial; and inflating the balloon preform into a balloon as it iscontinued to be exposed to said internal pressure at an increasedtemperature.

A method of creating a non-shortening catheter balloon with increasedburst pressures is provided comprising: wrapping a mandrel with ananisotropic film at a low angle to form a balloon preform; exposing theballoon preform to internal pressure at temperatures below melting pointof the film; inflating the balloon as it is continued to be exposed tosaid internal pressure and constant temperature; and wrapping theinflated balloon with an overwrap at an angle between 54 and 90 degreesto form a high pressure catheter balloon that is retractable.

A method of creating a non-shortening catheter balloon with increasedburst pressures is provided comprising: wrapping a mandrel with ananisotropic film at a low angle to form a balloon preform; removing themandrel; exposing the balloon preform to internal pressure attemperatures above ambient to soften or melt the film, inflating theballoon as it is continued to be exposed to said internal pressure andconstant temperature; and wrapping the inflated balloon helically withan anisotropic material at a high angle of between 54 and 90 degrees toform a high pressure catheter balloon.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a wrapped balloon of the present invention.

FIG. 2 shows a balloon material with a single side coating.

FIG. 3 shows a balloon material with a double sided coating.

FIG. 4 shows a schematic of a partially wrapped balloon.

FIG. 5 shows a cross section of wrapped balloon on a core.

FIG. 6 shows a cross section of wrapped balloon on a core with acigarette wrapped second balloon material pass.

FIG. 7 shows a cross section of wrapped balloon on a core with acigarette wrapped second balloon material pass and non-distendingregions.

FIG. 8 shows a cross section of wrapped balloon on a core with anoverlapped cigarette wrap of second balloon material pass.

FIG. 9 shows a mold-shaped catheter balloon with non-distensibleregions.

FIG. 10 shows a cross-section view of a wrapped balloon withnon-distensible regions.

DETAILED DESCRIPTION OF THE INVENTION

The balloon catheter of the present invention in its simplest formcomprises a catheter shaft having a longitudinal axis and an inflatableballoon affixed thereto. The balloon is comprised of at least twopasses. An individual pass is comprised of one or more layers ofmaterial which are laid at a similar angle in relation to thelongitudinal axis of the balloon. A layer is considered to be onethickness of balloon material which may be wrapped, folded, laid orweaved over, around, beside or under another thickness. A longitudinalpass comprises a distinctive layer or series of layers of material whichare wound to form a region or area distinct from surrounding oradjoining parts. For instance a pass may comprise multiple layers ofballoon material wrapped at a 90 degree angle relative to thelongitudinal axis. This exemplary pass may then be flanked by layers ofballoon material wrapped at dissimilar angles in relation to thelongitudinal axis, thus defining the boundary of the pass.

A pass of balloon material may be oriented helically, radially orlongitudinally. By layers of balloon material it is meant to includepieces, threads, layers, filaments, membranes, or sheets of suitableballoon material. In helically oriented layers, the material is orientedso to form a balanced force angle in relation to each other uponinflation. The layers may further be wound upon themselves in subsequentpasses. A balanced force balloon of the present invention is a balloonpossessing a combination of passes to create the strength to balance theradial force exerted by inflation pressures on the balloon vessel withrespect to the longitudinal forces exerted by inflation so that theballoon inflates to its desired diameter without any longitudinalmovement. One method of achieving a balanced-force-angle balloon is toorient the helical layers to approach the geometrically derived neutralangle value of 54.7 degrees. This neutral angle is derived frombalancing the forces in a thin walled pressure vessel where: 2× Axialstress=Hoop stress. The inflatable balloon of the present inventionexhibits both essentially radial symmetry upon inflation andnon-foreshortening. Radial symmetry is exhibited upon inflation as themovement of the balloon material away from the center point of the lumenin a direct radial fashion so that the balloon maintains a relativelyradial outward movement which resists twisting of the balloon surface asthe balloon inflates. By non-foreshortening it is meant that the lengthof the balloon does not change by more than ten percent upon inflationto a rated burst pressure. In preferred applications, the balloon doesnot change length by more than 5 percent upon inflation to a rated burstpressure. In further preferred applications, the balloon does not changelength by more than 2 percent upon inflation to a rated burst pressure.A radial symmetry upon inflation allows the balloon to exhibit an equalhydrostatic force on a vessel wall in clinical use. When used with astent or stent graft, an equal hydrostatic force allows uniformdeployment capability. Uniform stent deployment is preferred so thatless trauma is inflicted on the vessels and more efficient vesselscaffolding is achieved, as compared to other types of deployment.

In one embodiment as shown in FIG. 1, an inflatable device of thepresent invention comprises a catheter shaft 18 having a longitudinalaxis and an inflatable balloon 9 affixed to the shaft, the balloon hasan un-inflated length which remains relatively unchanged as the balloonis inflated and comprises at least two helical wrap passes of a balloonmaterial 6. The at least two passes may be fused together. The balloonhas a working length 15, shoulders 14, and wrapped balloon material 6 onthe legs 50 of the balloon. As shown in FIG. 2, the balloon material 6comprises a porous reinforcing polymer 1 and a polymer coating 2. Thepolymer coating is imbibed into the porous reinforcing polymer to form acontinuous polymer layer 12. The porous reinforcing polymer may comprisea fibrous reinforcement, a porous membrane such as, a polyolefin, afluoropolymer, a discontinuous phase of a polymer, or an orientedmicroporous reinforcement, such as ePTFE. In the present invention it isdesirable to use expanded PTFE (ePTFE) as a porous reinforcing polymer,allowing the balloon material to realize a matrix tensile value in onedirection greater than 690 megapascals; or preferably greater than 960megapascals; more preferably greater than 1,200 megapascals.

The oriented microporous reinforcement may be a fluoropolymer, apolyamide, a polyurethane, a polyester, a PEEK, a reinforced polymer, orany other suitable materials or combination of materials. The polymercoating 2 is imbibed throughout the porous reinforcing polymer and maycomprise a fluoropolymer, an elastomer, a urethane, a silicone, astyrene block copolymer, a fluoro-elastomer, a bioresorbable material orany other suitable polymer. As further shown in FIG. 1, the ballooncomprises a working length 15 between two shoulders 14 of the balloon.In a preferred embodiment, the balloon comprises at least one hoop passwrapped over the working length and a shoulder pass having a thicknessratio between the hoop layer and the shoulder layer of 2:1. The balloonmaterial layers forming the individual passes may be heated or set inposition relative to each other after each pass.

Typical low angle wrapped balloons tend to foreshorten as they inflateand the wrap angle rotates towards the neutral angle. Less obvious isthat the wrap layers also strain perpendicular to the wrap angle duringthe rotation caused by inflation. The growth in the wrap layer widthfollows this geometrically derived equation: (Width_(F)=Width_(I)×(cosθ_(F)/Cos θ_(I))²×(tan θ_(F)/tan θ₁) where F is final and I is initial,and θ is the angle of the helical wrap relative to the longitudinal axisof the balloon. This strain can exceed 500 percent in some balloonsdepending on the deflated to inflated ratio. Highly anisotropicmaterials are necessary to allow this perpendicular stain. The wraplayers when configured in accordance with the present invention, reset alow angle wrapped balloon at or near a balanced force angle whichprevents the layers from incurring transverse strain in subsequentballoon inflations. Additionally, the balloon exhibits essentiallyradial symmetry upon inflation. The balloon is wrapped by winding layersat opposing directions to one another until a desired thickness isobtained. The balloon material passes may be comprised of the samematerials or different materials. While the thickness of the materialsmay vary, for vascular use it is advantageous to use balloon materialthat is about 4-6 micrometers thick.

As shown in FIGS. 2 and 3, a balloon material comprising a polymer layer2 is coated on the porous reinforcement polymer 1 allowing the polymercoating to fill the void spaces of the porous reinforcement polymer 1.The polymer layer 2 may desirably fill the void spaces in the porousreinforcement polymer 1 to form a filled polymer layer 12. The polymerlayer 2 may be formed on one side of the porous reinforcing polymer 1(FIG. 2) or on both sides of the porous reinforcing polymer 1 (FIG. 3).The composite film 3 may further comprise a filler. The filler mayprovide benefits such as radio opaque marking or therapeutic value. Theballoon material may be cut into more narrow widths if necessary to formwrapping layers used in the balloon. An anisotropic material is used asa wrap layer in balloon passes consisting of wrap layer angles of lessthan about 55 degrees. However, if an overwrap pass is employed it maycomprise isotropic or anisotropic material depending on desiredapplications.

The composite film 3 of the present invention comprises a porousreinforcing layer and a continuous polymer layer as depicted in FIGS. 2and 3. The porous reinforcing polymer layer 1 is preferably a thinstrong porous membrane that can be made in sheet form. The porousreinforcing polymer can be selected from a group of polymers includingbut not limited to: olefin, PEEK, polyamide, polyurethane, polyester,polyethylene, and polytetrafluoroethylene. In a preferred embodiment theporous reinforcing polymer is expanded polytetrafluoroethylene (ePTFE)made in accordance with the general teachings of U.S. Pat. No. 5,476,589and U.S. patent application Ser. No. 11/334,243. In this preferredembodiment, the ePTFE membrane is anisotropic such that it is highlyoriented in the one direction. An ePTFE membrane with a matrix tensilevalue (matrix tensile stress or MTS) in one direction of greater than690 megapascals is preferred, and greater than 960 megapascals is evenmore preferred, and greater than 1,200 megapascals is most preferred.The exceptionally high MTS of ePTFE membrane allows the compositematerial to withstand very high hoop stress in the inflated balloonconfiguration. In addition, the high matrix tensile value of the ePTFEmembrane makes it possible for very thin layers to be used which reducesthe deflated balloon profile. A small profile is necessary for theballoon to be able to be positioned in small arteries or veins ororifices. In order for balloons to be positioned in some areas of thebody, the balloon catheter must be able to move through a small bendradius, and a thinner walled tube is typically much more supple andcapable of bending in this manner without creasing or causing damage tothe wall of the vessel.

The continuous polymer layer 2 of the present invention is coated ontoat least one side of the porous reinforcing polymer 1 as depicted inFIGS. 2 & 3. The continuous polymer layer is preferably an elastomer,such as but not limited to, aromatic and aliphatic polyurethanesincluding copolymers, styrene block copolymers, silicones, preferablythermoplastic silicones, fluoro-silicones, fluoroelastomer, THV andlatex. In one embodiment of the present invention, the continuouspolymer layer 2 is coated onto only one side of the porous reinforcingpolymer 1, as shown in FIG. 2. As depicted in FIG. 3, the continuouspolymer layer 2 is coated onto both sides of the porous reinforcingpolymer 1. In one aspect, the continuous polymer layer 2 is imbibed intothe porous reinforcing polymer 1 and the imbibed polymer 2 fills thepores of the porous reinforcing polymer 1 to form a composite 12.

The continuous polymer layer can be applied to the porous reinforcingpolymer through any number of conventional methods including but notlimited to, lamination, transfer roll coating, wire-wound bar coating,reverse roll coating, and solution coating or solution imbibing. In apreferred embodiment, the continuous polymer layer is solution imbibedinto the porous reinforcing polymer. In this embodiment, the continuouspolymer layer polymer is dissolved in a suitable solvent and coated ontoand throughout the porous reinforcing polymer using a wire-wound rodprocess. The coated porous reinforcing polymer is then passed through asolvent oven and the solvent is removed leaving a continuous polymerlayer coated onto and throughout the porous reinforcing polymer. In somecases, such as when silicone is used as the continuous polymer layer,the coated porous reinforcing polymer may not require the removal ofsolvent. In another embodiment, the continuous polymer layer is coatedonto at least one side of the porous reinforcing polymer and maintainedin a “green” state where it can be subsequently cured. For example, anultraviolet light (UV) curable urethane may be used as the continuouspolymer layer and coated onto the porous reinforcing polymer. Thecomposite film comprising the porous reinforcing polymer and the UVcurable urethane continuous polymer layer can then be wrapped to form atleast one layer of the balloon and subsequently exposed to UV light andcured.

In another aspect of this invention, the helically wrapped passes ofballoon material are bonded to each other. A preferred bonding techniqueis heat although other types of bonding may be used. The balloonmaterial is then annealed in the inflated state through the applicationof heat to reset the low angle wrap balloon perform at or near abalanced force angle.

As shown in FIGS. 4 and 5, the first balloon material 6 may be wrappedaround a core wire 4. The core wire 4 may be coated with a release agent5, such as an FEP coating or other suitable agent. The helical wraplayers are first laid across the longitudinal axis in one direction orpass. A second pass lays another helical wrap layer in the opposingdirection. Both passes 6 are oriented at an angle of less than or equalto about 55 degrees with respect to the longitudinal axis but inopposing directions. FIG. 5 shows that non-distensible layers 7 may bepresent to form non-distensible regions 8. The helically wrap layers ofa first balloon material pass may be bonded to a second balloon materialpass through the application of heat, or another suitable bondingtechnique. These balloon preforms are wrapped at a low angle tofacilitate sealing to a catheter shaft. The distensible region of thepreform is then inflated and the helical wrapped layers of the firstmaterial are reset at a balanced force angle through heating, solvating,annealing, or through a second material added while in the inflatedstate. The second material may be comprised of the same or differentmaterials as the first material.

In one preferred embodiment as shown in FIGS. 6 and 8, a balloonmaterial 6 is wrapped into at least two passes to form a balloon preformand then is fused and inflated to form the shape of a catheter balloon.The balloon material 6 is then held at balanced force angle by secondballoon material layer 11 which is cigarette wrapped around the firstballoon material at an angle greater than 54 degrees relative to thelongitudinal axis of the catheter balloon. It is preferred that two endsof the second balloon material overlap to form a longitudinally orientedseam 13, as shown in FIG. 8.

In another preferred embodiment as shown in FIGS. 7 and 9, a balloonmaterial 6 is wrapped into a low angle balloon preform. The balloon isinflated in an inflation mold 10 as shown in FIG. 9. The inflation mold10 is of a desired shape to form a catheter balloon which is then heldat balanced force angle by second pass of balloon material 11 that ishelically wrapped around the molded catheter balloon at an angle greaterthan 54 degrees but not greater than 90 degrees relative to thelongitudinal axis of the catheter balloon. A non-distensible region 8may be included in the balloon as shown in FIGS. 5, 7, and 9. Thenon-distending regions 8 are focal regions which are more resistant toradial dilatation allowing for reduction of load or sealing of aninflated balloon to an underlying catheter shaft. A non-distendingregion 8 comprises a plurality of non-distensible layers 7 which windaround the balloon material 6 and overlap to form an angle of between 0degrees to 90 degrees relative to the longitudinal axis of the balloon.The non-distending regions 8 are incorporated or integrated into thesurface of the balloon wall, into the balloon wall, or under the outermost surface of the balloon wall. The non-distending regions 8 are indirect continuity with the balloon wall and are virtuallyindistinguishable in form from the balloon wall in an un-inflated state.

The second balloon material 11 may be isotropic, having a relativelyequal strength in all directions or anisotropic having an orientedlongitudinal strength.

The balloons of the present invention expand from a low-profile deliveryconfiguration to an inflated configuration in a uniform concentricmanner over substantially its entire working length. The presentinvention is applicable for use with non-compliant or semi-compliantballoons.

In another embodiment, the inventive balloon comprises a balloonmaterial 6 wrapped into a low angle preform and inflated to form theshape of a catheter balloon which is then further wrapped and held at abalanced force angle by a pass or passes of second balloon materialoriented at an angle greater than 54 degrees with respect to thelongitudinal balloon axis. It is desirable to orient the second balloonmaterial helically in direction of the maximum hoop stress to create ahigh pressure balloon. It is desirable to use ePTFE as the porousreinforcing polymer in the composite film of a balloon layer to achievea maximum hoop stress of the helically wrapped layers in greater than400 megapascals. Even more desirable is achieving a maximum hoop stressof the helically wrapped layers in greater than 600 megapascals.

The balloon materials may comprise a filler if desired to alleviateleakage of the membrane or to deliver therapeutic agents. The filler maybe radio opaque or provide therapeutic value. The balloon may furthercomprise one or more integral non-distending regions, as describedabove. An integral non-distending region may be located between two ormore layers of balloon material or located on the surface of a balloonmaterial 6 to form a non-distending region 8 (see FIGS. 5 and 10).

FIG. 10 shows a core wire 4 with a release agent 5, a balloon material 6and a surface mounted non-distensible layer 7 forming a seal. Thenon-distending region, as depicted in FIG. 5, is formed by changing thewrapping angle of the balloon material layers to create a build up ofnon-distending passes. The non-distending passes overlap each othereither wholly or partially to form one or more non-distending regions 8on the wrapped distensible balloon. The non-distending regions 8 aresignificantly less compliant under distention force than a distensiblemain body of the balloon. The non-distending region may comprise thesame material as a distensible balloon material 6 or a differentmaterial. It is preferable that the non-distending region 8 undergoeslittle or no change in radial diameter upon introduction of distentionforce.

The present invention further contemplates that a balloon cathetercomprising a catheter shaft with a longitudinal axis and an inflatableballoon of the present invention affixed to the shaft. A catheterballoon of the present invention may be used in conjunction with astent. When at least the second balloon material exhibits a low modulus,the balloon material is able to pillow into the stent interstices. Thus,the pillow areas which fill in the interstices of a stent provide stentembedment prior to stent delivery. In this manner the stent is embeddedwithout the use of heat, and without balloon inflation.

A method of creating a non-shortening catheter balloon with increasedburst pressures is also provided, comprising wrapping a wire core with aplurality of balloon material layers or pieces at a angle of between 3and 54 degrees relative to the longitudinal axis of the balloon to forma balloon preform; exposing the plurality of balloon material layers toheat to bond them together; removing the core; and then further exposingthe balloon preform to internal pressure at a reflow temperature. Thereflow temperature is the temperature to soften or a melt point for thefilm or imbibing material; and inflating the balloon preform into aballoon as it is continued to be exposed to said internal pressure at anincreased temperature. At this point if desired the balloon may bewrapped with a second balloon material layer at a high angle of between54 and 90 degrees. The second balloon material may be fused to theinflated balloon by the application of heat or other desired bondingtechnique. The balloon is then removed from exposure to reflowtemperature and internal pressure to create a non-shortening balloon.When a second balloon material is used it may be fused to the inflatedballoon by the application of heat or other desired bonding technique.Further, an inflation mold may be used to inflate the balloon using heatand pressure so that a desired balloon shape results prior to passingthe second balloon material layer. The second balloon material may becigarette wrapped or helically wrapped.

A yet further embodiment of creating a non-shortening catheter balloonwith increased burst pressures is also provided, comprising wrapping amandrel with a plurality of anisotropic first balloon material layers ata low angle of between 3 and 54 degrees relative to the longitudinalaxis to form a balloon preform, these first balloon layers may beoriented in opposing directions relative to the longitudinal balloonaxis; exposing the plurality of balloon material layers to heat to bondthem together creating a preform; placing the balloon preform in a moldand exposing the balloon preform to internal pressure; inflating theballoon preform as it is continued to be exposed to said internalpressure creating a balloon; and removing the balloon from the mold; andwrapping the inflated balloon with a second balloon material layer at anangle between 54 and 90 degrees to form a high pressure catheterballoon. The second balloon material may be isotropic or anisotropic.The mandrel may be a wire or any other suitable core material to providea hollow body upon removal from the balloon material. In this method aballoon may be created with the addition of heat and pressure so that nomold is needed. Alternatively, as heat and pressure are added, theballoon may be inflated into a mold.

Additionally, it may be desirable in some shaped balloons to have acatheter shaft comprising a reinforced inner member located adjacent tothe longitudinal axis of the balloon and between the shaft and theballoon wherein the reinforced inner member is modulated to compensatefor shape shifting or pressure changes in the balloon so as to preventmovement of the catheter balloon upon inflation. The catheter shaft mayalso comprise an expandable pleated shaft section located adjacent tothe longitudinal axis of the balloon wherein the expandable pleatedshaft section is formed to compensate for movement or shifting in theballoon upon inflation. To increase the bonding of the seals of theshaped balloon, a catheter shaft comprising an outer seal dimensionhaving both convex portions and concave portions which provide anincreased surface area and increased seal strength when attached to theballoon ends.

The following examples are provided to illustrate the present invention.While particular embodiments of the present invention have beenillustrated and described herein, the present invention should not belimited to such illustrations and descriptions. It should be apparentthat changes and modifications may be incorporated and embodied as partof the present invention within the scope of the following claims andexamples.

EXAMPLES Example 1

The ePTFE membrane used to make the composite film was made inaccordance with the teaching in U.S. Pat. No. 5,476,589 to Bacino.Specifically, the ePTFE membrane was longitudinally expanded to a ratioof 55 to 1 and transversely expanded approximately 2.25 to 1, to producea thin strong membrane with fibrils oriented substantially in thelongitudinal direction, and a mass of approximately 3.5 g/m̂2 and athickness of approximately 6.5 micrometers.

The composite film was made by using a saturation coating processwhereby a solution of Tecothane TT-1085A polyurethane andtetrahydrofuran (THF) was coated onto the ePTFE membrane using awire-wound rod coating process. A 3% to 8% by weight solution ofTecothane TT-1085A polyurethane in THF was saturation coated onto theePTFE membrane to produce a composite film with approximately equalamounts of Tecothane TT-1085A polyurethane on either side of the ePTFEmembrane and a total polymer weight application of approximately 50% to60% of the total final composite film weight.

Example 2

A mechanically balanced composite film was made by using a wire-woundrod coating process whereby a solution of Tecothane TT-1085Apolyurethane and tetrahydrofuran (THF) was coated onto an ePTFEmembrane. The ePTFE membrane used to make the composite film was made inaccordance with the teachings of U.S. patent application Ser. No.11/334,243. Specifically, the ePTFE membrane was longitudinally expandedto a ratio of 15 to 1 and transversely expanded approximately 28 to 1,to produce a thin strong membrane with a mass of approximately 3.5 g/m²and a thickness of approximately 8 micrometers. A 3% to 8% by weightsolution of Tecothane TT-1085A polyurethane in THF was coated onto theePTFE membrane to produce a composite film with Tecothane TT-1085Apolyurethane on one side of the ePTFE membrane and throughout the ePTFEmembrane, and a total polymer weight application of approximately 40% to60% of the total final composite film weight.

Example 3

A mechanically balanced composite film was made by using a saturationcoating process whereby a solution of Tecothane TT-1085A polyurethaneand tetrahydrofuran (THF) was coated onto an ePTFE membrane using awire-wound rod coating process. The ePTFE membrane used to make thecomposite film was made in accordance with the teachings in Example (2).Specifically, the ePTFE membrane was longitudinally expanded to a ratioof 15 to 1 and transversely expanded approximately 28 to 1, to produce athin strong membrane with an mass of approximately 3.1 g/m² and athickness of approximately 8 micrometers. A 3% to 8% by weight solutionof Tecothane TT-1085A polyurethane in THF was saturation coated onto theePTFE membrane to produce a composite film with approximately equalamounts of Tecothane TT-1085A polyurethane on either side of the ePTFEmembrane and a total polymer weight application of approximately 40% to50% of the total final composite film weight.

Example 4

The composite balloons of the present invention were evaluated on aninflation tester (Interface Associates model PT3070, Laguna Nigel,Calif.). The inflation tester was filled with distilled, de-ionizedwater. A balloon was connected to the inflation tester and equilibratedin a water circulation bath (Polyscience Model 210, Niles, Ill.) at 37 Cfor 5 minutes. The balloons were cycled three times to 5 atmospheres ofpressure at a rate of 6 atmospheres per minute, held at 5 atmospheres ofpressure for 10 seconds, and then ramped back down at 6 atmospheres perminute. After cycling the pressure was increased in increments of 1atmosphere every 10 seconds. The diameter was recorded at each pressureincrement with a laser micrometer (Keyence Model LS-7501, WoodcliffLake, N.J.). The length was manually measured with a micrometer(Mitutoyo Absolute Digimatic 500-196, Aurora, Ill.) several times duringthe pressure ramp, and the pressure value was recorded for each lengthmeasurement taken.

Example 5

The inflatable balloon of the present invention was made by wrapping acomposite film of Tecothane TT-1085A polyurethane (Thermedics, Inc,Woburn, Mass.), and ePTFE membrane, as described in Example 1, over aFEP coated silver plated copper wire (Putnam Plastics LLC, Dayville,Conn.).

The 0.394 mm diameter wire core was deadsoft copper with silver platingand a 0.2 mm fluorinated ethylene-propylene (FEP) coating.

The composite film was slit to 5 mm wide and wrapped around the wire ata 4 to 5 degree angle from the longitudinal axis of the wire. Thewrapped wire was heated for approximately 5 to 30 seconds at 180 C afterwrapping. The wire was then wrapped with the composite film in theopposite direction at a 4 to 5 degree angle from the longitudinal axisof the wire and subsequently heated for approximately 5 to 30 seconds at180 C. The process of wrapping the wire in opposite directions andheating after each pass was repeated until a total of four passes ofwrapping was complete. The wrapped wire was wrapped around a pin framewith approximately 30 cm spaces between pins and approximately 180degrees of wrap around each pin and tied at the ends before being placedinto an oven and heated for approximately 30 minutes at 150 C, removed,and permitted to cool to ambient.

Example 6

From the balloon detailed in Example 5, approximately a 2.54 cm sectionof the composite hollow balloon tube was removed from either end of alonger section of the balloon. The exposed ends of the wire were clampedwith hemostats and pulled by hand until the wire had been stretchedapproximately 5 cm, at which point it was removed from the center of thetube. The plastic FEP coating was removed in a similar fashion, but wasstretched approximately 50 cm before it was removed from the balloon.

The hollow balloon was clamped on one side with a hemostat, and Monojectblunt needle with Aluminum luer lock hub (model # 8881-202389, SherwoodMedical, St. Louis Mo.) was inserted approximately 2 cm into the openend of the balloon. The hemostatic valve was tightened to seal theballoon, and was then attached to a Balloon Development Station #210A(Beahm Designs, Inc., Campbell, Calif.) with nozzle airflow is set to25-30 units, temperature to 140 C, air pressure to 2.0 atmospheres.

A piece of composite film as described in Example 1 was cut to 22 mm by47 mm in the longitudinal and transverse directions respectively. Thecomposite film was positioned with the longitudinal axis to run aroundthe circumference of the balloon and the edge running along the lengthof the balloon was lightly tacked to the balloon by gently touching aWeller EC1002 solder iron (Cooper Industries, Inc. Raleigh, N.C.) usinga Apollo Seiko power source (Model PPM, Apollo Seiko, Inc. Chatsworth,Calif.). The balloon was then allowed to cool for approximately 10seconds and the pressure was increased to approximately 4.0 atmospheres.The composite film was then carefully wrapped around the inflatedballoon in a cigarette fashion. The section of the composite film thatprotruded from the ends of the inflated balloon were pressed and twistedgently around the shoulder of the balloon. A second piece of compositefilm was cut 12 mm by 47 mm in the transverse and longitudinal directionrespectively. The composite film was positioned with the transverse axisto run around the circumference of the balloon and the edge runningalong the length of the balloon was lightly tacked to the balloon asdescribed above. The section of the composite film that protruded fromthe ends of the inflated balloon were pressed and twisted gently aroundthe shoulder of the balloon.

A 7 mm wide by 50 mm long strip of composite film was wrapped snugglyaround either end of the shoulders. The entire balloon was thensubjected to the heat zone of the heat box at 140 C for about 1 minutewhile maintaining approximately 4.0 atmospheres of pressure. Any visualimperfection such as a wrinkle was pressed down by hand from the outsidewhile the balloon was still hot and pressurized from the inside.

Using a Monoject blunt needle with Al Luer Lock Hub (Model 8881-202389,Sherwood Medical, St. Louis, Mo.), the wrapped balloon was subjected toan internal pressure of approximately 5.4 atmospheres at roomtemperature for 0.5-2.0 hours, and was subsequently removed from thepressure and cut to size by slicing both uninflated ends to theirdesired length.

Example 7

A 30.5 cm long section of the composite balloon as described in Example5 was cut and mounted onto a wrapper consisting of two chuck endscapable of clamping to the ends of the wire and a means for rotating thewire at variable speed. The balanced composite film as described inExample 2 was slit into a 6.35 mm wide strip and six layers were wrappedover the balloon in two locations leaving a 33 mm wide section betweenthe over-wrapped areas. These over-wrapped regions or non-distensibleseals were used to terminate the inflated balloon region. Theover-wrapped balloon was then heated in a convection oven at 150° C. for30 minutes unrestrained and subsequently removed from the oven andallowed to cool to room temperature.

The wire and the FEP coating over the wire were removed from the balloonover wire construction. Approximately a 2.54 cm section of the compositehollow balloon tube was removed from either end of a 30.5 cm longsection of the balloon. The exposed ends of the wire were clamped withhemostats and pulled by hand until the wire had been stretchedapproximately 5 cm, at which point it was removed from the center of thetube. The plastic FEP coating was removed in a similar fashion, but wasstretched approximately 50 cm before it was removed from the balloon.

The composite hollow balloon was then connected to an Encore 26inflation device (Boston Scientific Scimed, Maple Grove, Minn., Catalog#15-105). The balloon was located in a 2.0 mm diameter polycarbonatemold and pressurized to 10 atmospheres and held at pressure for 5minutes. The balloon was deflated, removed from the 2.0 mm diameter moldand positioned in a 2.5 mm diameter polycarbonate mold and re-inflatedto 10 atmospheres and held for 5 minutes. The process of inflating theballoon in the mold provided a more uniform surface on the balloon.

The composite balloon was then mounted onto a small gauge needle andconnected to a rotary union (Dynamic Sealing Technologies, Inc, HamLake, Minn.), and the other end was connected to the rotating end of thewrapper described above. The balloon was inflated through the rotaryunion using the Encore 26 inflation device to 10 atmospheres with water.The composite film described was slit to approximately 7.6 mm and wasused as the second balloon material layer wrapping. The slit compositefilm was helically wound around the inflated balloon at approximately 75to 85 degrees relative to the longitudinal axis of the balloon. Theprocess of wrapping the balloon was repeated at the same angle but inthe opposite direction.

Using a Weller WSD81 solder gun unit (Cooper Industries, Inc. Raleigh,N.C.), equipped with a large blunt solder tip set to a 250 set-point,the second balloon material layer wrapping was fused to the firstballoon material layer wrapping. The solder tip was pressed lightlyagainst the surface of the balloon while the balloon rotated at 20 rpm,and was slowly traversed along the length of the inflated balloon. Therotation of the balloon was stopped and the solder tip was then pressedlightly against the surface of the inflated balloon and traversed alongthe length of the balloon at four locations each 90 degrees around thecircumference of the balloon. Pressure was relieved and balloon removedfrom rotary union chucks and trimmed to final length.

This procedure produced a non-shortening wrapped balloon that wheninflated to 10 or more atmospheres of pressure created a 3.0 mm diameterand 25 mm long balloon between the non-distensible over-wrapped regions.

Example 8

The core wire and the FEP coating over the core wire were removed fromthe composite balloon over wire construction described in Example 5.

Approximately a 2.54 cm long section of the composite hollow balloontube was removed from either end of a 30.5 cm long section of theballoon over wire construction. The exposed ends of the wire wereclamped with hemostats and pulled by hand until the wire had beenstretched approximately 5 cm, at which point it was removed from thecenter of the tube. The plastic FEP coating was removed in a similarfashion, but was stretched approximately 50 cm before it was removedfrom the balloon. A composite hollow balloon tube was produced with afirst layer wrapping material at a low (4 to 5 degree) angle of wrap.

A 15.25 cm long section of the composite hollow balloon tube was tiedinto a knot and clamped with a hemostat on one end. The opposite end wasslipped through a Qosina male touhy borst with spin lock fitting(#80343, Qosina Corporation, Edgewood, N.Y.), and a Monoject bluntneedle with Aluminum luer lock hub (model # 8881-202389, SherwoodMedical, St. Louis Mo.) was inserted approximately 2.0 cm into theballoon. The hemostatic valve was tightened to seal the balloon, and wasthen attached to a Balloon Development Station Model 210A (BeahmDesigns, Inc., Campbell, Calif.). The nozzle airflow was set to 25-30units and the temperature was set to 140 C, air pressure to 2.58atmospheres. The air pressure was turned on, the center 40 mm longregion to be inflated, was subjected to heat for about 2-3 minutesresulting in a balloon with a diameter of 2.85 mm and a length of. Thediameter was checked with a Mitutoyo Laser Scan Micrometer ModelLSM-3100 (Mitutoyo America Corp, Aurora, Ill.) while in the inflatedstate. The resulting balloon had a diameter of 2.85 mm and an inflatedlength of 27 mm.

Using an Monoject blunt needle with Aluminum luer lock hub (model #8881-202389, Sherwood Medical, St. Louis Mo.) dispensing needle, theballoon was subjected to an internal pressure of 5.44 atmospheres atroom temperature for approximately 1 hour. The Inflation Pressure andlength results are shown below.

A B C 1426-49-3G 4th Cycle 1419-101A-2 4th Cycle 1419-102-6B 4th CyclePressure Length Diam Pressure Length Diam Pressure Length Diam (atm)(mm) (mm) (atm) (mm) (mm) (atm) (mm) (mm) 0 26.38 2.54 0 30.04 1.71 025.64 2.72 0.07 26.15 2.53 0.06 30.05 1.66 0.06 25.57 2.72 1 26.15 2.890.99 30.3 2.14 0.99 25.57 2.88 2 24.75 3.04 1.98 30.51 2.65 1.98 25.572.91 2.99 24.75 3.05 2.97 30.58 2.66 2.97 25.57 2.91 3.99 24.75 3.053.97 30.58 2.67 3.97 25.57 2.92 4.98 24.75 3.04 4.97 30.12 2.66 4.9625.57 2.93 5.99 24.75 3.03 5.96 30.12 2.68 5.97 25.57 2.95 6.97 25.353.04 6.97 30.12 2.72 6.96 25.57 2.95 7.97 25.35 3.08 7.97 29.93 2.747.94 25.57 2.96 8.91 24.41 3.17 8.97 29.93 2.76 8.95 25.69 2.97 9.9325.43 3.27 9.96 29.75 2.78 9.96 26.06 2.98 11.01 25.76 3.42 10.96 29.752.83 10.95 26.06 3 11.96 29.49 2.84 11.94 26.06 3.02 12.95 29.32 2.8812.93 26.06 3.02 13.97 29.19 2.89 13.92 26.08 3.04 14.94 28.92 2.91 14.926.39 3.06 15.96 29.92 2.93 15.89 26.4 3.1 16.97 29.16 2.95 16.9 26.393.11 17.95 28.93 3 17.8 26.39 3.17 18.91 28.93 3.03 19.93 28.93 3.0520.92 28.93 3.07 21.96 28.93 3.1 22.92 29.02 3.18

Example 9

Tensile break load was measured using in INSTRON 1122 tensile testmachine equipped with flat-faced grips and a 0.445 kN load cell. Thegauge length was 5.08 cm and the cross-head speed was 50.8 cm/min. Thesample dimensions were 2.54 cm by 15.24 cm. For longitudinal MTSmeasurements, the larger dimension of the sample was oriented in themachine, also known as the down-web direction. For the transverse MTSmeasurements, the larger dimension of the sample was orientedperpendicular to the machine direction, also known as the cross-webdirection. Each sample was weighed using a Mettler Toledo Scale ModelAG204, then the thickness of the samples was taken using the KaferFZ1000/30 thickness gauge. The samples were then tested individually onthe tensile tester. Three different sections of each sample weremeasured. The average of the three maximum load (i.e., the peak force)measurements was used. The longitudinal and transverse MTS werecalculated using the following equation:

MTS(psi)=(maximum load/cross-section area)*(bulk density(PTFE))/densityof the porous membrane),

wherein the bulk density of PTFE is taken to be 2.2 g/cc.

1. A method of creating a non-shortening balloon with increased burstpressures, said balloon comprising: a) wrapping a mandrel with at leastone first balloon material to form a balloon preform; b) exposing thefirst balloon material to heat; c) removing the mandrel; d) exposing theballoon preform to internal pressure at a reflow temperature; e)inflating the balloon preform into a balloon as it is continued to beexposed to said internal pressure at an increased temperature; and f)removing heat and internal pressure.
 2. The method of claim 1 whereinthe wire core of step (a) is wrapped with film at a low angle of between3 and 54 degrees.
 3. The method of claim 1 further comprising step(f)(1) inflating the non-shortening balloon and wrapping with a secondballoon material pass at a high angle of between 54 and 90 degrees. 4.The method of claim 1 further comprising step (f)(2) passing heat tobond said second balloon pass to the inflated balloon.
 5. The method ofclaim 1 wherein the heat and pressure are added and the balloon isinflated into a mold.
 6. The method of claim 1 wherein the heat andpressure are added and the balloon is inflated without a mold.
 7. Themethod of claim 1 wherein the second balloon material is cigarettewrapped.
 8. The method of claim 1 wherein the second balloon material ishelically wrapped.
 9. A method of creating a non-shortening catheterballoon with increased burst pressures, comprising: a) wrapping a wirecore with a plurality of first balloon material layer at a low angle; b)further wrapping with a plurality of first balloon material at a lowangle in the opposite direction of a) relative to the longitudinalballoon axis; c) exposing the plurality of first balloon material layersto heat to bond them together creating a preform; d) removing the wirecore; e) placing the balloon preform in a mold and exposing the balloonpreform to internal pressure; f) inflating the balloon preform as it iscontinued to be exposed to said internal pressure creating a balloon; g)removing the balloon from the mold; h) wrapping the inflated balloonwith second balloon material layers oriented at an angle between 54 and90 degrees; and i) bonding the first and second balloon material. 10.The method of claim 9 wherein the second balloon material is isotropic.11. The method of claim 9 wherein the second balloon material isanisotropic.
 12. The method of claim 9 where heat is used to bond saidsecond balloon material to first balloon material.
 13. The method ofclaim 9 wherein the first balloon material is an isotropic